We don't know a lot of things about David Woodman's death.
We don't know if Woodman's friends are telling the truth when they say that the 22-year-old's only offenses were drinking beer in public and making a sarcastic comment to some police officers standing on a corner and that those officers responded by picking up Woodman, slamming him into a fence, and then shoving him down to the pavement.
We don't know if Woodman attempted to flee and then resisted arrest with a force that required multiple officers to subdue him, as police contend.
We don't know how long he lay face down on Brookline Avenue, hands cuffed behind his back, before the officers noticed he wasn't breathing.
We don't know exactly when those officers started CPR. The police report says they did so immediately, but ambulance records show they didn't put in an urgent call for at least six minutes after they cuffed Woodman.
We don't know if those six minutes made the difference between life and death.
We don't know whether Woodman's heart condition ultimately killed him.
And yet, even though we don't know the answers to any of these questions, Police Commissioner Edward F. Davis has come to an important conclusion: There was no brutality.
"While our investigation is still preliminary," he said Monday, "it appears from the evidence that we have reviewed thus far that officers did not use excessive force."
How does he know this? Why, his police officers told him so, of course. And other witnesses backed them up. And the officers involved did not use their spray or batons.
All of which, apparently, cancels out the accounts by Woodman's friends, who said they were forced to leave the area because the police, who had already surrounded Woodman, had threatened to arrest them.
All nine of the police officers directly involved in the arrest went to the hospital that night with stress-related complaints.
They are all back at work now, and maybe they regret the decisions they took in the first hour of June 18.
Maybe they wish that when Woodman walked by them, in a part of the city where there was little going on after the Celtics' NBA championship win, and reportedly said, "Wow, it seems like there's a lot of crime on this corner," that they had just told him to zip it, empty his cup, and be on his way.
Maybe they wish that department procedures did not allow for people to be subdued with such force.
They are probably in a world of pain and worry.
Any police chief worth his salt would want to back up those officers. But Davis should have resisted that impulse.
The department and the Suffolk district attorney are at the beginning of their investigation, one which the commissioner himself vowed will be exhaustive, impartial, and transparent. Why come to any conclusions before the thing is complete?
It may turn out that police acted entirely appropriately that night. But right now, all we really know is that David Woodman spent six minutes in police custody, and now he is dead.
Despite Davis's expressions of condolence, his statement smacked of circled wagons.
The stakes here are enormously high.
This is the third death at a Boston sports celebration and the second during the course of Boston police crowd control. It has been fewer than four years since 21-year-old Victoria Snelgrove was killed by a police officer's pepper pellet gun on Lansdowne Street, during a riotous celebration of the Red Sox World Series win.
Snelgrove's death rocked the department, shaking the city's faith in its police force. Woodman's death has the potential to do the same.
Davis is as much a steward of that faith as he is a leader to his officers.
He owes us more.
Yvonne Abraham is a Globe columnist. Her email is Abraham@globe.com.